Fan array fan section in air-handling systems

ABSTRACT

A fan array fan section in air-handling system includes a plurality of fan units arranged in a fan array. Each fan unit is positioned within a fan unit chamber/cell. Each fan unit chamber/cell has at least one acoustically absorptive insulation surface. The insulation surfaces of the fan unit chamber/cells together form a coplanar silencer. Sound waves from the fan units passing through the insulation surface at least partially dissipate as they pass therethrough. In one preferred embodiments the fan unit chamber/cell is a cell having a frame that supports the insulation surface.

The present application is a continuation-in-part application of patentapplication Ser. No. 10/806,775, filed Mar. 22, 2004, and entitled FANARRAY FAN SECTION IN AIR-HANDLING SYSTEMS. patent application Ser. No.10/806,775 is a nonprovisional application claiming the benefit under 35USC Section 119(e) of U.S. Provisional Patent Application Ser. No.60/554,702, filed Mar. 20, 2004, and entitled FAN ARRAY FAN SECTION INAIR-HANDLING SYSTEMS. Patent application Ser. No. 10/806,775 is anonprovisional application claiming the benefit under 35 USC Section119(e) of U.S. Provisional Patent Application Ser. No. 60/456,413, filedMar. 20, 2003, and entitled FAN ARRAY FAN SECTION IN AIR-HANDLINGSYSTEMS. The present application is a continuation-in-part applicationof PCT Patent Application Serial Number PCT/US2004/008578, filed Mar.19, 2004, and entitled FAN ARRAY FAN SECTION IN AIR-HANDLING SYSTEMS.The present application is based on and claims priority from theseapplications, the disclosures of which are hereby expressly incorporatedherein by reference.

BACKGROUND OF INVENTION

The present invention is directed to a fan array fan section utilized inan air-handling system.

Air-handling systems (also referred to as an air handler) havetraditionally been used to condition buildings or rooms (hereinafterreferred to as “structures”). An air-handling system is defined as astructure that includes components designed to work together in order tocondition air as part of the primary system for ventilation ofstructures. The air-handling system may contain components such ascooling coils, heating coils, filters, humidifiers, fans, soundattenuators, controls, and other devices functioning to meet the needsof the structures. The air-handling system may be manufactured in afactory and brought to the structure to be installed or it may be builton site using the necessary devices to meet the functioning needs of thestructure. The air-handling compartment 102 of the air-handling systemincludes the inlet plenum 112 prior to the fan inlet cone 104 and thedischarge plenum 110. Within the air-handling compartment 102 issituated the fan unit 100 (shown in FIGS. 1 and 2 as an inlet cone 104,a fan 106, and a motor 108), fan frame, and any appurtenance associatedwith the function of the fan (e.g. dampers, controls, settling means,and associated cabinetry). Within the fan 106 is a fan wheel (not shown)having at least one blade. The fan wheel has a fan wheel diameter thatis measured from one side of the outer periphery of the fan wheel to theopposite side of the outer periphery of the fan wheel. The dimensions ofthe handling compartment 102 such as height, width, and airway lengthare determined by consulting fan manufacturers data for the type of fanselected.

FIG. 1 shows an exemplary prior art air-handling system having a singlefan unit 100 housed in an air-handling compartment 102. For exemplarypurposes, the fan unit 100 is shown having an inlet cone 104, a fan 106,and a motor 108. Larger structures, structures requiring greater airvolume, or structures requiring higher or lower temperatures havegenerally needed a larger fan unit 100 and a generally correspondinglylarger air-handling compartment 102.

As shown in FIG. 1, an air-handling compartment 102 is substantiallydivided into a discharge plenum 110 and an inlet plenum 112. Thecombined discharge plenum 110 and the inlet plenum 112 can be referredto as the airway path 120. The fan unit 100 may be situated in thedischarge plenum 110 as shown), the inlet plenum 112, or partiallywithin the inlet plenum 112 and partially within the discharge plenum110. The portion of the airway path 120 in which the fan unit 100 ispositioned may be generically referred to as the “fan section”(indicated by reference numeral 114). The size of the inlet cone 104,the size of the fan 106, the size the motor 108, and the size of the fanframe (not shown) at least partially determine the length of the airwaypath 120. Filter banks 122 and/or cooling coils (not shown) may be addedto the system either upstream or downstream of the fan units 100.

For example, a first exemplary structure requiring 50,000 cubic feet perminute of air flow at six (6) inches water gage pressure would generallyrequire a prior art air-handling compartment 102 large enough to house a55 inch impeller, a 100 horsepower motor, and supporting framework. Theprior art air-handling compartment 102, in turn would be approximately92 inches high by 114 to 147 inches wide and 106 to 112 inches long. Theminimum length of the air-handling compartment 102 and/or airway path120 would be dictated by published manufacturers data for a given fantype, motor size, and application. Prior art cabinet sizing guides showexemplary rules for configuring an air-handling compartment 102. Theserules are based on optimization, regulations, and experimentation.

For example, a second exemplary structure includes a recirculation airhandler used in semiconductor and pharmaceutical clean rooms requiring26,000 cubic feet per minute at two (2) inches water gage pressure. Thisstructure would generally require a prior art air-handling system with aair-handling compartment 102 large enough to house a 44 inch impeller, a25 horsepower motor, and supporting framework. The prior artair-handling compartment 102, in turn would be approximately 78 incheshigh by 99 inches wide and 94 to 100 inches long. The minimum length ofthe air-handling compartment 102 and/or airway path 120 would bedictated by published manufacturers data for a given fan type, motorsize and application. Prior art cabinet sizing guides show exemplaryrules for configuring an air-handling compartment 102. These rules arebased on optimization, regulations, and experimentation.

These prior art air-handling systems have many problems including thefollowing exemplary problems:

-   -   Because real estate (e.g. structure space) is extremely        expensive, the larger size of the air-handling compartment 102        is extremely undesirable.    -   The single fan units 100 are expensive to produce and are        generally custom produced for each job.    -   Single fan units 100 are expensive to operate.    -   Single fan units 100 are inefficient in that they only have        optimal or peak efficiency over a small portion of their        operating range.    -   If a single fan unit 100 breaks down, there is no air        conditioning at all.    -   The low frequency sound of the large fan unit 100 is hard to        attenuate.    -   The high mass and turbulence of the large fan unit 100 can cause        undesirable vibration.

Height restrictions have necessitated the use of air-handling systemsbuilt with two fan units 100 arranged horizontally adjacent to eachother. It should be noted, however, that a good engineering practice isto design air handler cabinets and discharge plenums 110 to besymmetrical to facilitate more uniform air flow across the width andheight of the cabinet. Twin fan units 100 have been utilized where thereis a height restriction and the unit is designed with a high aspectratio to accommodate the desired flow rate. As shown in the Greenheck“Installation Operating and Maintenance Manual,” if side-by-sideinstallation was contemplated, there were specific instructions toarrange the fans such that there was at least one fan wheel diameterspacing between the fan wheels and at least one-half a fan wheeldiameter between the fan and the walls or ceilings. The Greenheckreference even specifically states that arrangements “with less spacingwill experience performance losses.” Normally, the air-handling systemand air-handling compartment 102 are designed for a uniform velocitygradient of 500 feet per minute velocity in the direction of air flow.The two fan unit 100 air-handling systems, however, still substantiallysuffered from the problems of the single unit embodiments. There was norecognition of advantages by increasing the number of fan units 100 fromone to two. Further, the two fan unit 100 section exhibits a non-uniformvelocity gradient in the region following the fan unit 100 that createsuneven air flow across filters, coils, and sound attenuators.

It should be noted that electrical devices have taken advantage ofmultiple fan cooling systems. For example, U.S. Pat. No. 6,414,845 toBonet uses a multiple-fan modular cooling component for installation inmultiple component-bay electronic devices. Although some of theadvantages realized in the Bonet system would be realized in the presentsystem, there are significant differences. For example, the Bonet systemis designed to facilitate electronic component cooling by directing theoutput from each fan to a specific device or area. The Bonet systemwould not work to direct air flow to all devices in the direction ofgeneral air flow. Other patents such as U.S. Pat. No. 4,767,262 to Simonand U.S. Pat. No. 6,388,880 to El-Ghobashy et al. teach fan arrays foruse with electronics.

Even in the computer and machine industries, however, operating fans inparallel is taught against as not providing the desired results exceptin low system resistance situations where fans operate in near freedelivery. For example, Sunon Group has a web page in which they show twoaxial fans operating in parallel, but specifically state that if “theparallel fans are applied to the higher system resistance that [an]enclosure has, . . . less increase in flow results with parallel fanoperation.” Similar examples of teaching against using fans in parallelare found in an article accessible from HighBeam Research's: library(http://stati.highbeam.com) and an article by Ian McLeod accessible at(http://www.papstplc.com).

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to a fan array fan section in anair-handling system. The fan array fan section includes a plurality offan units arranged in a fan array. Each fan unit is positioned within afan unit chamber/cell. Each fan unit chamber/cell has at least oneacoustically absorptive insulation surface. The insulation surfaces ofthe fan unit chambers/cells together form a coplanar silencer. Soundwaves from the fan units passing through the insulation surface at leastpartially dissipate as they pass therethrough. In one preferredembodiments the fan unit chamber/cell is a cell having a frame thatsupports the insulation surfaces.

The present invention is also directed to a fan array fan section in anair-handling system that includes a plurality of fan units arranged in afan array and positioned within an air-handling compartment. Onepreferred embodiment may include an array controller programmed tooperate the plurality of fan units at peak efficiency. The plurality offan units may be arranged in a true array configuration, a spacedpattern array configuration, a checker board array configuration, rowsslightly offset array configuration, columns slightly offset arrayconfiguration, or a staggered array configuration.

The foregoing and other objectives, features and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a side view of an exemplary prior art air-handling systemhaving a single large fan unit within an air-handling compartment.

FIG. 2 is a perspective view of an exemplary prior art large fan unit.

FIG. 3 is a side view of an exemplary fan array fan section in anair-handling system of the present invention having a plurality of smallfan units within an air-handling compartment.

FIG. 4 is a plan or elevation view of a 4×6 exemplary fan array fansection in an air-handling system of the present invention having aplurality of small fan units within an air-handling compartment.

FIG. 5 is a plan or elevation view of a 5×5 exemplary fan array fansection in an air-handling system of the present invention having aplurality of small fan units within an air-handling compartment.

FIG. 6 is a plan or elevation view of a 3×4 exemplary fan array fansection in an air-handling system of the present invention having aplurality of small fan units within an air-handling compartment.

FIG. 7 is a plan or elevation view of a 3×3 exemplary fan array fansection in an air-handling system of the present invention having aplurality of small fan units within an air-handling compartment.

FIG. 8 is a plan or elevation view of a 3×1 exemplary fan array fansection in an air-handling system of the present invention having aplurality of small fan units within an air-handling compartment.

FIG. 9 is a plan or elevation view of an alternative exemplary fan arrayfan section in an air-handling system of the present invention in whicha plurality of small fan units are arranged in a spaced pattern arraywithin an air-handling compartment.

FIG. 10 is a plan or elevation view of an alternative exemplary fanarray fan section in an air-handling system of the present invention inwhich a plurality of small fan units are arranged in a checker boardarray within an air-handling compartment.

FIG. 11 is a plan or elevation view of an alternative exemplary fanarray fan section in an air-handling system of the present invention inwhich a plurality of small fan units are arranged in rows slightlyoffset array within an air-handling compartment.

FIG. 12 is a plan or elevation view of an alternative exemplary fanarray fan section in an air-handling system of the present invention inwhich a plurality of small fan units are arranged in columns slightlyoffset array within an air-handling compartment.

FIG. 13 is a plan or elevation view of a 5×5 exemplary fan array fansection in an air-handling system of the present invention running at52% capacity by turning a portion of the fans on and a portion of thefans off.

FIG. 14 is a plan or elevation view of a 5×5 exemplary fan array fansection in an air-handling system of the present invention running at32% capacity by turning a portion of the fans on and a portion of thefans off.

FIG. 15 is a side view of an alternative exemplary fan array fan sectionin an air-handling system of the present invention having a plurality ofstaggered small fan units within an air-handling compartment.

FIG. 16 is a perspective view of an exemplary fan array using a gridsystem into which fan units are mounted.

FIG. 17 is a perspective view of an exemplary fan array using a gridsystem or modular units each of which includes a fan units mountedwithin its own fan unit chamber.

FIG. 18 is a cross-sectional view of an exemplary insulated grid arraysystem or modular unit system having interior surfaces made fromacoustically absorptive material.

FIGS. 19-23 are cross-sectional view of an exemplary insulated gridarray system or modular unit system having interior surfaces made fromacoustically absorptive material showing sound wave reaction.

FIG. 24 is a wave form diagram illustrating the principle of wavecancellation.

FIG. 25 is a perspective view of an exemplary array of dampeners thatmay be positioned either in front of or behind the fan units.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a fan array fan section in anair-handling system. As shown in FIGS. 3-12, the fan array fan sectionin the air-handling system uses a plurality of individual single fanunits 200. In one preferred embodiment, the fan units 200 are arrangedin a true array (FIGS. 4-8), but alternative embodiments may include,for example, alternative arrangements such as in a spaced pattern (FIG.9), a checker board (FIG. 10), rows slightly offset (FIG. 11), orcolumns slightly offset (FIG. 12). As the present invention could beimplemented with true arrays and/or alternative arrays, the term “array”is meant to be comprehensive.

The fan units 200 in the fan array of the present invention may bespaced as little as 20% of a fan wheel diameter. Optimum operatingconditions for a closely arranged array may be found at distances as lowas 30% to 60% of a fan wheel diameter. By closely spacing the fan units200, more air may be moved in a smaller space. For example, if the fanwheels of the fan units 200 have a 20 inch fan wheel diameter, only a 4inch space (20%) is needed between the outer periphery of one fan wheeland the outer periphery of the adjacent fan wheel (or a 2 inch spacebetween the outer periphery of a fan wheel and an the adjacent wall orceiling).

By using smaller fan units 200 it is possible to support the fan units200 with less intrusive structure (fan frame). This can be compared tothe large fan frame that supports prior art fan units 100 and functionsas a base. This large fan frame must be large and sturdy enough tosupport the entire weight of the prior art fan units 100. Because oftheir size and position, the known fan frames cause interference withair flow. In the preferred embodiment, therefore, the fan units 200 ofthe fan array may be supported by a frame that supports the motors 108with a minimum restriction to air flow.

As mentioned in the Background, others have tried using side-by-sideinstallation of two fan units 100 arranged horizontally adjacent to eachother within an air-handling system. As is also mentioned in theBackground, fan arrays have been used in electronic and computerassemblies. However, in the air-handling system industry, it has alwaysbeen held that there must be significant spacing between thehorizontally arranged fan wheels and that arrangements with less spacingwill experience performance losses. A single large fan moves all the airin a cabinet. Using two of the same or slightly smaller fans caused theair produced by one fan to interfere with the air produced by the otherfan. To alleviate the interference problem, the fans had to be spacedwithin certain guidelines—generally providing a clear space between thefans of a distance of at least one wheel diameter (and a half a wheeldiameter to an adjacent wall). Applying this logic, it would not havemade sense to add more fans. And even if additional fans had been added,the spacing would have continued to be at least one wheel diameterbetween fans. Further, in the air-handling system industry, verticallystacking fan units would have been unthinkable because the means forsecuring the fan units would not have been conducive to such stacking(they are designed to be positioned on the floor only).

It should be noted that the plenum fan is the preferred fan unit 200 ofthe present invention. In particular, the APF-121, APF-141, APF-161, andAPF-181 plenum fans (particularly the fan wheel and the fan cone)produced by Twin City Fan Companies, Ltd. of Minneapolis, Minn., U.S.has been found to work well. The reason that plenum fans work best isthat they do not produce points of high velocity such as those producedby axial fans and housed centrifugal fans and large plenum fans.Alternative embodiments use known fan units or fan units yet to bedeveloped that will not produce high velocity gradients in the directionof air flow. Still other embodiments, albeit less efficient, use fanunits such as axial fans and/or centrifugal housed fans that have pointsof high velocity in the direction of air flow.

In the preferred embodiment, each of the fan units 200 in the fan arrayfan section in the air-handling system is controlled by an arraycontroller 300 (FIGS. 13 and 14). In one preferred embodiment, the arraycontroller 300 may be programmed to operate the fan units 200 at peakefficiency: In this peak efficiency embodiment, rather than running allof the fan units 200 at a reduced efficiency, the array controller 300turns off certain fan units 200 and runs the remaining fan units 200 atpeak efficiency. In an alternative embodiment, the fan units 200 couldall run at the same power level (e.g. efficiency and/or flow rate) ofoperation.

Another advantage of the present invention is that the array controller300 (which may be a variable frequency drive (VFD)) used for controllingfan speed and thus flow rate and pressure, could be sized for the actualbrake horsepower of the fan array fan section in the air-handlingsystem. Since efficiency of the fan wall array can be optimized over awide range of flow rates and pressures, the actual operating powerconsumed by the fan array is substantially less than the actualoperating power consumed by the comparable prior art air-handlingsystems and the array controller's power could be reduced accordingly.The array controller 300 could be sized to the actual power consumptionof the fan array where as the controller (which may have been a variablefrequency drive) in a traditional design would be sized to the maximumnameplate rating of the motor per Electrical Code requirements. Anexample of a prior art fan design supplying 50,000 cubic feet per minuteof air at 2.5 inches pressure, would require a 50 horsepower motor and50 horsepower controller. The new invention will preferably use an arrayof fourteen 2 horsepower motors and a 30 horsepower array controller300.

This invention solves many of the problems of the prior art air-handlingsystems including, but not limited to real estate, reduced productioncosts, reduced operating expenses, increased efficiency, improved airflow uniformity, redundancy, sound attenuation advantages, and reducedvibration.

Controllability

As mentioned, preferably each of the fan units 200 in the fan array fansection in the air-handling system is controlled by an array controller300 (FIGS. 13 and 14) that may be programmed to operate the fan units200 at peak efficiency. In this peak efficiency embodiment, rather thanrunning all of the fan units 200 at a reduced efficiency, the arraycontroller 300 is able to turn off certain fan units 200 and run theremaining fan units 200 at peak efficiency. Preferably, the arraycontroller 300 is able to control fan units 200 individually, inpredetermined groupings, and/or as a group as a whole.

For example, in the 5×5 fan array such as that shown in FIGS. 5,13, and14, a person desiring to control the array may select desired airvolume, a level of air flow, a pattern of air flow, and/or how many fanunits 200 to operate; Turning first to air volume, each fan unit 200 ina 5×5 array contributes 4% of the total air. In variable air volumesystems, which is what most structures have, only the number of fanunits 200 required to meet the demand would operate. A control system(that may include the array controller 300) would be used to take fanunits 200 on line (an “ON” fan unit 200) and off line (an “OFF” fan unit200) individually. This ability to turn fan units 200 on and off couldeffectively eliminate the need for a variable frequency drive.Similarly, each fan unit 200 in a 5×5 array uses 4% of the total powerand produces 4% of the level of air flow. Using a control system to takefan units 200 on line and off line allows a user to control power usageand/or air flow. The pattern of air flow can also be controlled if thatwould be desirable. For example, depending on the system it is possibleto create a pattern of air flow only around the edges of a cabinet orair only at the top. Finally, individual fan units 200 may be taken online and off line. This controllability may be advantageous if one ormore fan units 200 are not working properly, need to be maintained (e.g.needs general service), and/or need to be replaced. The problematicindividual fan units 200 may be taken off line while the remainder ofthe system remains fully functional. Once the individual fan units 200are ready for use, they may be brought back on line.

A further advantage to taking fan units 200 on and off line occurs whenbuilding or structure control systems require low volumes of air atrelatively high pressures. In this case, the fan units 200 could bemodulated to produce a stable operating point and eliminate the surgeeffects that sometimes plague structure owners and maintenance staff.The surge effect is where the system pressure is too high for the fanspeed at a given volume and the fan unit 200 has a tendency to go intostall.

Examples of controllability are shown in FIGS. 13 and 14. In the fanarray fan section in the air-handling system shown in FIG. 13, the arraycontroller 300 alternates “ON” fan units 200 and “OFF” fan units 200 ina first exemplary pattern as shown so that the entire system is set tooperate at 52% of the maximum rated air flow but only consumes 32% offull rated power. These numbers are based on exemplary typical fanoperations in a structure. FIG. 14 shows the fan array fan section inthe air-handling system set to operate at 32% of the maximum rated airflow but only consumes 17% of full rated power. These numbers are basedon exemplary typical fan operations in a structure. In this embodiment,the array controller 300 creates a second exemplary pattern of “OFF” fanunits 200 and “ON” fan units 200 as shown.

Real Estate

The fan array fan section in the air-handling section 220 of the presentinvention preferably uses (60% to 80%) less real estate than prior artdischarge plenums 120 (with the hundred series number being prior art asshown in FIG. 1 and the two hundred series number being the presentinvention as shown in FIG. 3) in air-handling systems. Comparing theprior art (FIG. 1) and the present invention (FIG. 3) shows a graphicalrepresentation of this shortening of the airway path 120, 220. There aremany reasons that using multiple smaller fan units 200 can reduce thelength of the airway path 120, 220. For example, reducing the size ofthe fan unit 100, 200 and motor 108, 208 reduces the length of thedischarge plenum 110, 210. Similarly, reducing the size of the inletcone 104, 204 reduces the length of the inlet plenum 112, 212. Thelength of the discharge plenum 110, 210 can also be reduced because airfrom the fan array fan section in the air-handling system of the presentinvention is substantially uniform whereas the prior art air-handlingsystem has points of higher air velocity and needs time and space to mixso that the flow is uniform by the time it exits the air-handlingcompartment 102, 202. (This can also be described as the higher staticefficiency in that the present invention eliminates the need forsettling means downstream from the discharge of a prior art fan systembecause there is little or no need to transition from high velocity tolow velocity.) The fan array fan section in the air-handling systemtakes in air from the inlet plenum 212 more evenly and efficiently thanthe prior art air-handling system so that the length of the inlet plenum112, 212 may be reduced.

For purposes of comparison, the first exemplary structure set forth inthe Background of the Invention (a structure requiring 50,000 cubic feetper minute of air flow at a pressure of six (6) inches water gage) willbe used. Using the first exemplary structure, an exemplary embodiment ofthe present invention could be served by a nominal discharge plenum 210of 89 inches high by 160 inches wide and 30 to 36 inches long (ascompared to 106 to 112 inches long in the prior art embodiments). Thedischarge plenum 210 would include a 3×4 fan array fan section in theair-handling system such as the one shown in FIG. 6) having 12 fan units200. The space required for each exemplary fan unit 200 would be arectangular cube of approximately 24 to 30 inches on a side depending onthe array configuration. The airway path 220 is 42 to 48 inches (ascompared to 88 to 139 inches in the prior art embodiments).

For purposes of comparison, the second exemplary structure set forth inthe Background of the Invention (a structure requiring 26,000 cubic feetper minute of air flow at a pressure of two (2) inches water gage) willbe used. Using the second exemplary structure, an exemplary embodimentof the present invention could be served by a nominal discharge plenum210 of 84 inches high by 84 inches wide, and and 30 to 36 inches long(as compared to 94 to 100 inches long in the prior art embodiments). Thedischarge plenum would include a 3×3 fan array fan section in theair-handling system (such as the one shown in FIG. 7) having 9 fan units200. The space required for-each exemplary fan unit 200 would be arectangular cube of approximately 24 to 30 inches on a side depending onthe array configuration. The airway path 220 is 42 to 48 inches (ascompared to 71 to 95 inches in the prior art embodiments).

Reduced Production Costs

It is generally more cost effective to build the fan array fan sectionin the air-handling system of the present invention as compared to thesingle fan unit 100 used in prior art air-handling systems. Part of thiscost savings may be due to the fact that individual fan units 200 of thefan array can be mass-produced. Part of this cost savings may be due tothe fact that it is less expensive to manufacture smaller fan units 200.Whereas the prior art single fan units 100 were generally custom builtfor the particular purpose, the present invention could be implementedon a single type of fan unit 200. In alternative embodiments, theremight be several fan units 200 having different sizes and/or powers(both input and output). The different fan units 200 could be used in asingle air-handling system or each air-handling system would have onlyone type of fan unit 200. Even when the smaller fan units 200 are custommade, the cost of producing multiple fan units 200 for a particularproject is almost always less that the cost of producing a single largeprior art fan unit 100 for the same project. This may be because of thedifficulties of producing the larger components and/or the cost ofobtaining the larger components necessary for the single large prior artfan unit 100. This cost savings also extends to the cost of producing asmaller air-handling compartment 202.

In one preferred embodiment of the invention, the fan units 200 aremodular such that the system is “plug and play.” Such modular units maybe implemented by including structure for interlocking on the exteriorof the fan units 200 themselves. Alternatively, such modular units maybe implemented by using separate structure for interlocking the fanunits 200. In still another alternative embodiment, such modular unitsmaybe implemented by using a grid system into which the fan units 200may be placed.

Reduced Operating Expenses

The fan array fan section in the air-handling system of the presentinvention preferably are less expensive to operate than prior artair-handling systems because of greater flexibility of control and finetuning to the operating requirements of the structure. Also, by usingsmaller higher speed fan units 200 that require less low frequency noisecontrol and less static resistance to flow.

Increased Efficiency

The fan array fan section in the air-handling system of the presentinvention preferably is more efficient than prior art air-handlingsystems because each small fan unit 200 can run at peak efficiency. Thesystem could turn individual fan units 200 on and off to preventinefficient use of particular fan units 200. It should be noted that anarray controller 300 could be used to control the fan units 200. As setforth above, the array controller 300 turns off certain fan units 200and runs the remaining fan units 200 at peak efficiency.

Redundancy

Multiple fan units 200 add to the redundancy of the system. If a singlefan unit 200 breaks down, there will still be cooling. The arraycontroller 300 may take disabled fan units 200 into consideration suchthat there is no noticeable depreciation in cooling or air flow rate.This feature may also be useful during maintenance as the arraycontroller 300 may turn off fan units 200 that are to be maintainedoffline with no noticeable depreciation in cooling or air flow rate. Abypass feature, discussed below, uses and enhances the redundancy of thesystem.

Sound Attenuation Advantages

The high frequency sound of the small fan units 200 is easier toattenuate than the low frequency sound of the large fan unit. Becausethe fan wall has less low frequency sound energy, shorter less costlysound traps are needed to attenuate the higher frequency sound producedby the plurality of small fan units 200 than the low frequency soundproduced by the single large fan unit 100. The plurality of fan units200 will each operate in a manner such that acoustic waves from eachunit will interact to cancel sound at certain frequencies thus creatinga quieter operating unit than prior art systems.

Reduced Vibration

The multiple fan units 200 of the present invention have smaller wheelswith lower mass and create less force due to residual unbalance thuscausing less vibration than the large fan unit. The overall vibration ofmultiple fan units 200 will transmit less energy to a structure sinceindividual fans will tend to cancel each other due to slight differencesin phase. Each fan unit 200 of the multiple fan units 200 manage asmaller percentage of the total air handling requirement and thusproduce less turbulence in the air stream and substantially lessvibration.

Alternative Embodiments

As mentioned, in one preferred embodiment of the invention, the fanunits 200 are modular such that the system is “plug and play.” Suchmodular units may be implemented by including structure for interlockingon the exterior of the fan units 200 themselves. Alternatively, suchmodular units may be implemented by using separate structure forinterlocking the fan units 200. In still another alternative embodiment,such modular units may be implemented by using a grid system into whichthe fan units 200 may be placed.

FIG. 16 shows an embodiment using an exemplary grid system 230 intowhich the fan units 200 may be placed. In this embodiment the grid maybe positioned and/or built within the air-handling compartment 202. Thefan units 200 may then be positioned into the grid openings. Oneadvantage of this configuration is that individual fan units 200 may beeasily removed, maintained, and/or replaced. This embodiment uses anexemplary unique motor mount 232 that supports the motor 208 withoutinterfering with air flow therearound. As shown, this exemplary motormount 232 has a plurality of arms that mount around the fan inlet cone204. It should be noted that the dimensions of the grid are meant to beexemplary. The grid may be constructed taking into consideration thatthe fan units 200 in the present invention may be spaced with as littleas 20% of a fan wheel diameter between the fan units 200.

FIG. 17 shows an embodiment using either a grid system or modular units240 using separate structure (not shown) for interlocking the fan units200. In this exemplary embodiment, each of the fan units 200 are mountedon a more traditional motor mount 242 within its own fan unit chamber244. In one preferred embodiment, the fan unit 200 and motor mount 242are preferably suspended within their own fan unit chamber 244 such thatthere is an air relief passage 246 therebelow. This air relieve passage246 tends to improve air flow around the fan units 200.

The fan unit chambers 244 shown in FIG. 17 may include one or moreinterior surface lined with an acoustically absorptive material or“insulation surface” 248. Similarly, the fan unit cells 244′ shown inFIGS. 18-23 may include one or more interior surface made from anacoustically absorptive material or “insulation surface” 248. Goingagainst conventional industry wisdom that surfaces cannot be placed inclose proximity with the fan units 200, the present invention places oneor more insulation surfaces 248 at least partially around each fan unit200 without disrupting air flow. The insulation surfaces 248 may includeone or more of the sides, top, bottom, front, or back. Exemplary typesof insulation include, but are not limited to traditional insulationboard (such as that made from inorganic glass fibers (fiberglass) aloneor with a factory-applied foil-scrim-kraft (FSK) facing or afactory-applied all service jacket (ASJ)) or alternative insulation suchas open cell foam such as that disclosed in U.S. patent application Ser.No. 10/606,435, which is assigned to the assignee of the presentinvention, and which the disclosure of which is hereby incorporated byreference herein. Together, the insulation surfaces 248 of the fan unitchambers/cells 244, 244′ tend to function as a coplanar silencer. Someof the benefits of using the coplanar silencer include (1) no addedairway length for splitters, (2) no pressure drop, and/or (3) relativelylow cost. The acoustic advantages of this and other embodiments make thepresent invention ideal for use in concert halls, lecture halls,performing arts centers, libraries, hospitals, and other applicationsthat are acoustically sensitive.

FIGS. 18-23 show an exemplary insulated grid system or modular unitsystem interior surfaces are made from acoustically absorptive materialor “insulation surface” 248. In this embodiment, each fan unit cell 244′preferably has a sturdy frame 250 that supports the insulation surfaces248. In one preferred embodiment the frame would form only the edges ofa cube-shaped fan unit cell 244′ and the insulation surfaces 248 wouldform the sides (e.g. top, bottom, and/or sides) of the cube-shaped fanunit cell 244′. In alternative preferred embodiments, the frame mayinclude additional structure or braces for support and/or strength.Together, the insulation surfaces 248 of the fan unit cells 244′ tend tofunction as a coplanar silencer. This is shown graphically in FIGS.19-23 where the coplanar silencer (formed by the insulation surfaces248) reduces the sound wave reaction as the sound waves travel throughthe insulation surfaces 248. For example, in FIG. 19, the central fanunit 200 a is loudest in its own fan unit cell 244′. As the sound of thefan spreads radially, it at least partially dissipates as it passesthrough the surrounding insulation surfaces 248. This is showngraphically as the sound wave circles being darkest in the central fanunit cell 244′ and lighter in the surrounding fan unit cells 244′. Theresult is that the sound from the central fan unit 200 a that eventuallyemanates from the system is softer than sound that would emanate from asystem without the coplanar silencer. In FIG. 20, the first side fanunit 200 b is loudest in its own fan unit cell 244′. As the sound of thefan spreads radially, it at least partially dissipates as it passesthrough the surrounding insulation surfaces 248. This is showngraphically as the sound wave circles being darkest in the central fanunit cell 244′, lighter in the surrounding fan unit cells 244′, andstill lighter in fan unit cells 244′ more distant from the originatingfan unit 200 b. The result is that the sound from the fan unit 200 bthat eventually emanates from the system is softer than sound that wouldemanate from a system without the coplanar silencer. FIG. 21 shows thefirst side fan unit 200 b, a second side fan unit 200 c, and theirrespective sound waves. As shown graphically in FIG. 24, anotherprinciple of the present invention is that as the sound waves interact,there is a degree of wave cancellation such that the waves areself-extinguishing. FIG. 24 shows wave A and an opposite wave B that areopposites and therefore interact to form a flat wave A+B. If waves arenot exactly opposite, then the combined wave will not be flat, but wouldhave some wave cancellation. This is a basic wave principle of which thepresent invention is able to avail itself. The result of wavecancellation is that the sound from the fan units 200 b and 200 c thateventually emanates from the system is softer than sound that wouldemanate from a system without the coplanar silencer. FIG. 22 emphasizesa first corner fan unit 200 d and its wave pattern. FIG. 23 emphasizesboth the first corner fan unit 200 d and a second corner fan unit 200 band their respective wave patterns. The analysis of FIGS. 22 and 23would be similar to that of FIGS. 20 and 21 respectively. It should benoted that in the preferred embodiment, more than two fans might berunning simultaneously and all the running fans would have wavepatterns. The wave patterns of all the running fans would be able totake advantage of both the dissipation (as they pass though surroundinginsulation surfaces 248) and wave cancellation of the coplanar silencer.

Although FIG. 17 shows the discharge plenum 210 positioned within thefan unit chambers 244, alternative embodiments of fan unit chambers 244could enclose the inlet plenum 212, or at least partially enclose boththe inlet plenum 212 and the discharge plenum 210. Still otheralternative embodiments of fan unit chambers 244 may have grid or wiresurfaces (that increase the safety of the present invention) or be open(that would reduce costs).

Bypass Feature

Multiple fan units enable the array to operate at a range of flow ratesfrom full flow to partial flow where each fan contributes 1/N air flow(where N equals the number of fans). Most direct drive fan systemsoperate at speeds other than full synchronous motor speed in order tomatch the heating or cooling requirements of the structure. Speedcontrol is normally maintained using variable frequency drives. Sincevariable frequency drives are electronic devices, each drive operatingwithin an air handling structure has a certain probability of failure.In a traditional air handling system, if the VFD fails the air handlerwill either shut down or be operated at full synchronous speed of themotor in what is known as bypass mode. In traditional systems fan unitsin the air handler have to be throttled back through some mechanicalmeans in order to limit pressure and flow to meet the buildingrequirements. Mechanical throttling in bypass mode on traditionalsystems creates excessive noise and reduces fan efficiency. The presentinvention overcomes this problem by allowing for a change in the fanarray output by turning certain fans off to meet the design point. Thearray can be tailored to meet the flow and pressure requirement withoutthe need for mechanical throttling and subsequent added noise andreduction in efficiency.

Dampeners

FIG. 25 shows an array of dampeners 260 that may be positioned either infront of or behind the fan units 200 to at least partially prevent backdrafts. In the shown exemplary embodiment, the dampeners 260 include aplurality of plates, each plate positioned on its own pivot. In theshown exemplary embodiment, the plurality of plates slightly overlapeach other. The shown embodiment is constructed such that when air isflowing through the fan units 200, the plates are in the open positionand when the air stops, gravity pulls the plates into the closedposition. Preferably, each of the dampeners 260 operates independentlysuch that if some of the fan units 200 are ON and some of the fan units200 are OFF, the dampeners 260 can open or close accordingly. Althoughshown as a simple mechanical embodiment, alternative embodiments couldinclude Structure that is controlled electronically and/or remotely fromthe dampeners 260.

It should be noted that FIG. 4 shows a 4×6 fan array fan section in theair-handling system having twenty-four fan units 200, FIG. 5 shows a 5×5fan array fan section in the air-handling system having twenty-five fanunits 200, FIG. 6 shows a 3×4 fan array fan section in the air-handlingsystem having twelve fan units 200, FIG. 7 shows a 3×3 fan array fansection in the air-handling system having nine fan units 200, and FIG. 8shows a 3×1 fan array fan section in the air-handling system havingthree fan units 200. It should be noted that the array may be of anysize or dimension of more than two fan units 200. It should be notedthat although the fan units 200 may be arranged in a single plane (asshown in FIG. 3), an alternative array configuration could contain aplurality of fan units 200 that are arranged in a staggeredconfiguration (as shown in FIG. 15) in multiple planes. It should benoted that cooling coils (not shown) could be added to the system eitherupstream or downstream of the fan units 200. It should be noted that,although shown upstream from the fan units 200, the filter bank 122, 222could be downstream.

It should be noted that an alternative embodiment would use ahorizontally arranged fan array. In other words, the embodiments shownin FIGS. 3-15 could be used horizontally or vertically or in anydirection perpendicular to the direction of air flow. For example, if avertical portion of air duct is functioning as the air-handlingcompartment 202, the fan array may be arranged horizontally. Thisembodiment would be particularly practical in an air handlingcompartment for a return air shaft.

It should be noted that the fan section 214 may be any portion of theairway path 220 in which the fan units 200 are positioned. For example,the fan units 200 may be situated in the discharge plenum 210 (asshown), the inlet plenum 212, or partially within the inlet plenum 212and partially within the discharge plenum 210. It should also be notedthat the air-handling compartment 202 may be a section of air duct.

It should be noted that many of the features and properties associatedwith the fan unit chambers 244 (FIG. 17) would be identical to orsimilar to properties of the fan unit cells 244′ (FIGS. 18-23).

The terms and expressions that have been employed in the foregoingspecification are used as terms of description and not of limitation,and are not intended to exclude equivalents of the features shown anddescribed or portions of them. The scope of the invention is defined andlimited only by the claims that follow.

1. A fan array fan section in air-handling compartment which is part ofan air-handling for conditioning the air of a structure, said fan arrayfan section comprising: (a) a plurality of fans units; (b) saidplurality of fan units arranged in a fan array; (c) each of saidplurality of fans units positioned within a fan unit chamber/cell; (d)each fan unit chamber/cell having at least one acoustically absorptiveinsulation surfaces; (e) said insulation surface of said fan unitchamber/cells together form a co-planar silencer; wherein (f) each ofsaid plurality of fan units is suspended within a fan unit chamber/cellsuch that there is an air relief passage which is isolated from theremainder of said fan unit chamber/cells so that a portion of the airdrawn by said fan unit passed through said air relief passage withoutpassing through said fan unit.
 2. A fan array section in an air-handlingcompartment which is part of an air-handling system for conditioning theair of a structure, said fan array fan section comprising: (a) aplurality of fans units; (b) said plurality of fan units arranged in afan array; (c) each of said plurality of fans units positioned within afan unit chamber/cell which substantially surrounds said fan unit; (d)each fan unit chamber/cell having at least one acoustically absorptiveinsulation surfaces; (e) said each fan unit chamber/cell being arrangedwithin an air-handling compartment such that the air from all of saidfan units is mixed before it enters the structure; wherein; and (f) eachof said plurality of fan units is suspended within a fan unitchamber/cell such that there is an air passageway therebelow.
 3. A fanarray fan section in air-handling system comprising: (a) at least threefan units; (b) each of said at least three fan units positioned within afan unit chamber/cell which substantially surrounds said fan unit; (c)each fan unit's chamber/cell having at least one insulating surface; (d)said at least three fan units arranged in a fan array; (e) wherein saidfan unit chamber/cell is cube-shaped; (f) said cube having a frame whichforms four edges of said cube; and (g) said insulation surfaces areindependent of said frame and from the portion of said cube not formedby said frame.
 4. The fan array section in a air-handling system ofclaim 3, said insulation surface of said fan unit chamber/cell togetherforming a co-planar silencer
 5. The fan array section in a air-handlingsystem of claim 3, wherein each said insulation surface is acousticallyabsorptive material.
 6. The fan array section in a air-handling systemof claim 3, wherein sound waves from said fan units passing through saidinsulation surfaces are at least partially dissipated as they passtherethrough.
 7. The fan array fan section in air-handling system ofclaim 3, wherein each of said at least three fan units is suspendedwithin a fan unit chamber/cell such that there is an air relief passagetherebelow.
 8. The fan array fan section in air-handling system of claim3, wherein said at least three fan units are a plurality of fan unitsarranged in a fan array configuration selected from the group consistingof: (a) a true array configuration; (b) a spaced pattern arrayconfiguration; (c) a checker board array configuration; (d) rowsslightly offset array configuration; (e) columns slightly offset arrayconfiguration; and (f) a staggered array configuration.
 9. The fan arrayfan section in an air-handling system of claim 3, wherein said at leastthree fan units are plenum fans including at least two verticallyarranged fan units.
 10. The fan array fan section in an air-handlingsystem of claim 3, wherein each of said at least three fan units ismounted in a grid system.
 11. The fan array fan section in anair-handling system of claim 3, said fan unit chamber/cells beingmodular units for in a modular unit system.